BENG 186B: Principles of Bioinstrumentation Design Lecture 15 Electrochemical Biosensors: pH, PO2, and PCO2 References Webster, Ch. 10 (Sec. 10.1-10.2).

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ellixisjulioSticky NoteSame electrode: only voltage contribution comes from nerst potential (permeable only to H+ ions only)

Measure pH by knowing pH HCL,

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ellixisjulioSticky NoteCo2 is charge neutral...no nernst potential

ellixisjulioSticky NoteNote: pH is pH of sample with pH of HCL buffer being 0 (1M solution of HCL). If pH of HCL is less than 1M, need to account for this in the equation (use nernst equation)

ellixisjulioSticky NoteNote: this equation assumes pH of HCL buffer is 1M, if this isn't the case, use the pH equation

ellixisjulioSticky NotePlatinum is inert: platinum electrodee is polarized

Ag/AgCl electrode nonpolarizable because AgCl layer can take or accept electrons

ellixisjulioSticky Notevoltage divider, creates a high effective resistance

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ellixisjulioSticky Note0.7 because at that voltage, the O2 concentration calibration curves have the largest gaps between different O2 concentration